BTO migration blog

Spring and autumn are exciting times for anyone who watches birds. Here on this blog we will make predictions about when to expect migrant arrivals and departures, so that you know when and where to see these well-travelled birds.

Friday, 27 April 2012

North and west, east and south divide.

It has very much been a week in which migration has been a
game of two halves, with south and east coast watchpoints having had a fairly
quiet time as far as visible migration and grounded migrants are
concerned. In contrast, during the early
part of the week, Fair Isle, Shetland, and Bardsey, Gwynedd, had their busiest
days of the spring so far.

Some birds have been getting through the heavy rainstorms
south of the UK. In the south, more Nightingales
arrived back on territory, birds could be heard throughout southern Britain. Cuckoos continued to trickle in, along
with a small number of Whitethroats and Grasshopper
Warblers. Hirundines continued to arrive too but the numbers for the time
of the year are low. Seawatchers in the south did experience a good passage of Great and Arctic Skuas, along with a small number of Pomarine Skuas. Arctic Terns were also still much in evidence and were joined at many sites by Little Gulls and the odd Black Tern.

Pomarine Skua by Joe Pender

Migration in the north and the west has been much more in
evidence. At the beginning of the week a large number of Robins, Dunnocks, Song Thrushes and Ring Ouzels arrived on Fair Isle, along with three Tree Pipits, a Blue Headed Wagtail, ninety-one Wheatears, four Swallows,
Two Wrynecks and singles of Hoopoe and Common Crane. At the same time Bardsey was teeming with migrants,
which included over two-hundred Willow Warblers,
over one-hundred Swallows, around
eighty Blackcaps and eleven Grasshopper Warblers.

Wryneck by Jill Pakenham

Wales also held the lion’s share of southern European
migrants. A Little Bittern was found
in Pembrokeshire, Ceredigion hosted a Kentish
Plover and six White Storks were
seen over Colwyn Bay.

It is interesting to look at the distribution of migrants
this week and relate them to the weather we have been experiencing. The birds
that arrived on Fair Isle did so when the wind turned east/south-easterly, and
those on Bardsey when the wind was from the north.

It could be that
these migrants drifted east in the westerly airflow that southern Europe have
been experiencing as weather fronts arrived from the Atlantic. Having drifted
east it is likely that they then made their way north on the wrong side of the
North Sea, the weather here has been more settled at times.

As they made their
way north the anti-cyclonic weather fronts would find them in a more easterly
airflow and by utilising this they would make their way back across the North
Sea to the UK, arriving much further north than they might have been aiming for.
This might help to explain a busy north and a quiet south migration-wise this
week.

Looking at the weather forecast for this weekend, Saturday
morning looks like the time to be out and about in search of migrants, as the
winds south of the UK will be lighter than they have been for a week or so. By
Saturday afternoon a low pressure system is due to cross central France,
bringing heavy rain and fairly strong winds with it. It could be that Sunday
will see a repeat performance of earlier in the week with the north and west
again being the place to be.

Friday, 20 April 2012

Even though the weather has been challenging for northward bound migrants, particularly in southern Europe, small numbers have still trickled in in during the week, with the exception of Ring Ouzel and Arctic Tern, which arrived in force.

Arctic Tern by Andy Mason

The early part of the week saw the continued Ring Ouzel arrival but as it tailed off towards the middle of the week, Arctic Terns took over. Flocks of this marine tern were seen migrating through the Midlands, with one flock of eighty birds lingering on Wednesday afternoon at Attenborough Nature Reserve, Nottinghamshire. Accompanying these were a small number of Little Gulls and the first Black Terns of the spring.

Arctic and Common Tern can be difficult to separate. See the BTO identification video for some useful tips.

As expected, most of the migrant action has been in the south, however Fair Isle, Shetland, saw its first Swallow and Tree Pipit of the spring.

Two Turtle Doves were found in Cambridgeshire, a few Whitethroats arrived and Reed Warblers can be heard in most southern reedbeds, albeit still in small numbers.

Despite the north and westerly airflow and very stormmy weather around the Mediterranean, southern overshoots have been well represented this week. With a Kentish Plover, Little Bittern and Black Kite, Wales was the place to be. Five new Hoopoes were found in southern Britain, along with two more Black kites, in Devon and Hertfordshire, and the two Black-winged Stilts from last week still putting in appearances.

Black-winged Stilt by Neil Calbrade

Common Sandpipers also put in an appearance with small groups seen at a few south coast sites. In general though it has been a fairly quiet week for the time of the year. However, it looks like there might be a small window in the weather in Europe on Saturday afternoon/Sunday morning, which could open the floodgates for those birds that are held-up further south, before stormy Atlantic weather returns on Monday to perhaps close them again.

Tuesday, 17 April 2012

This weekend’s cold north-easterly airflow wasn’t ideal for summer migrants heading back to the UK. However, birds did arrive, with Ring Ouzel being the most notable. Most of these were seen in the south but birds reached as far north as Glen Strathfarrar, Highland. In several counties flocks of Ring Ouzels reached into double figures, with fourteen being seen together at Pegsdon, Beds. This arrival is reflected nicely in the BirdTrack reporting rate.

Ring Ouzel by Tommy Holden

At this time of the year, Ring Ouzels can turn up on migration almost anywhere. Check-out the latest BTO identification video to listen to the differences between Ring Ouzel and Blackbird song, and other tips on identifying this enigmatic thrush.

South coast visible migration watchers were also rewarded with a steady arrival of Swallows and Willow Warblers, whilst smaller numbers of Redstarts, Yellow Wagtails and Grasshopper Warblers also made landfall. Some migrants are being held-up though, as illustrated in an email we received from Rod Leslie in the Pyrenees

"I was at Aiguamolls de l'Emporda just south of the Pyrenees yesterday (16 April) in a howling westerly gale & temperatures down to 5 degrees C. Migrants completely pinned down with large flocks of Hirundines looking very tired. In several hides where leeward windows had been left open large numbers of Swallows were sheltering - see the attached photo. They were so tired it was possible to quietly share the hide with them."

Hide full of sheltering Swallows

Aiguamolls de l'Emporda

The first multiple arrival of Nightingale was also obvious, with five singing males together in one Hampshire woodland. This spring the BTO is conducting a Nightingale survey to map all singing males.

With northerly winds dominating it is hardly surprising that Mediterranean overshoots were thin on the ground. However, at least two Hoopoes were reported, in Norfolk and Worcestershire, and two Black-winged Stilts braved the unseasonable spring chill in Dorset and Lincolnshire.

Wind, rain and cool weather had put a dampener on migration at Falsterbo over the previous week or so. The last 5 days have seen a change in the weather — southeasterly winds and warmer temperatures — and with the change in weather has come a wave of migrating birds. Robins are still the most obvious (we ringed 250 on Saturday) but we've also trapped our first trans-Saharan migrants; our first Willow Warbler on Thursday and our first Lesser Whitethroat on Sunday. Moreover, we finally got our first (and so far only) Blackcap of the spring.

Lesser Whitethroat by Stephen Menzie

Swallows, Wheatears, Ring Ouzels, Tree Pipits and Ospreys have all been seen with increasing frequency over the last few days. Falsterbo has already hosted a male Redstart — an early bird by Swedish standards. Sandwich Terns have become a constant background presence as they pass along the shore close to the lighthouse. Sunday saw a Pallid Harrier passing over the peninsular — one of the birds seen here last autumn on its way back north?

Scarce short-distance migrants ringed in the lighthouse garden have included a Hawfinch and several Firecrests (it's been an exceptionally good spring for Firecrests here in southern Sweden). 3,000 Eiders passing Sweden's most southerly point was a spectacle worth seeing — migration in action!

Friday, 13 April 2012

Having spent the last week or so on the south coast of Kent, full of anticipation for the wonderful spectacle of visible spring migration that I was going to enjoy, the final result was rather disappointing.

Clear blue skies and very light winds for ten consecutive days meant that any migrants that were arriving were too high to see, and the absence of moderate wind, cloud cover and drizzle (I must have been one of the few parents over the Easter break praying for these conditions, at least for a couple of days) meant there was also very few grounded migrants. On the plus side, those migrants that did arrive were presumably able to continue on their journeys directly to their breeding grounds.

Willow Warbler by Neil Calbrade

So what did happen? Further west along the south coast the weather conditions were much more mixed. Under thick cloud cover and moderate north-westerly wind, Portland Bird Observatory experienced its biggest falls this spring so far. On the last day of March there was a fall of around 3,000 Phylloscs (Willow Warblers and Chiffchaffs), 500 Blackcaps, 75 Wheatears, 12 Redstarts, 6 Ring Ouzels and 4 Pied Flycatchers, along with a steady arrival of small numbers of hirundines (Swallows, House Martins and Sand Martins).

One hundred and fifty miles to the east the picture was very different. On the same day under clear blue skies and no wind, I counted 5 Willow Warblers, 15 Chiffchaffs, 12 Wheatears, two Ring Ouzels and no Redstarts or hirundines.

So, migrants have been arriving, some such as Willow Warbler, Chiffchaff and Blackcap, in large numbers, However, for other species the arrival has been very light. For the time of year many of our summer visitors are worryingly absent. There are very few Swallows and Sand Martins around. Whitethroats and Sedge Warblers are also conspicuous by their absence too. This is probably down to southern Europe experiencing poor weather during the last week. Southern Spain and Portugal have had hailstorms, heavy rain and cool northerly winds. These conditions would be more than enough to bring migration to a halt.

With unsettled weather and a northerly airflow forecast for the next few days, migration will be slow. Birds will still arrive in small numbers and coastal watchpoints could see moderate falls as tired bird make landfall. The winds are due to be lighter on Sunday, so this could be the day to be out and about.